The present disclosure relates to an image processing apparatus which performs rasterization processing based on data written in a page description language (PDL). The present disclosure also relates to a method for controlling the image processing apparatus.
There are printing apparatuses which print based on data received from a computer. A computer transmits data in which printing content is written in a page description language. A printing apparatus which has received data generates print image data according to a described definition (command). Print image data is, for example, a bitmap data. When generating print image data, some printing apparatuses image characters. In this case, a printing apparatus generates character image data for each character. The printing apparatus pastes generated character image data to a page to generate print image data. Here, some printing apparatuses store the generated image data of each character in a cache memory. Reusing the data stored in the cache memory helps reduce the number of times of generating character image data.
As described below, there is a known technique by which character image data is stored in a cache memory. Some image forming apparatuses have a font cache of an LRU (least recently used) type, and, depending on whether the frequency of use of a character image is equal to or higher than a threshold value, judges whether or not to cache a character image at the top position in the font cache.
When rasterization (drawing) processing is performed based on data written in a page description language, texts (characters, words) may be imaged. Commands requesting imaging and texts to be imaged are embedded in data. Based on the commands and the texts, imaging of characters is performed character by character from the top of a page.
When a character is imaged, based on font data, character image data is generated. The generated character image data is pasted to a proper position in a page. The character is thus imaged. For example, image data of the character A is generated, and the generated image data of the character A is pasted. Generated character image data may be stored in a cache area. For example, a part of a RAM is allocated to the cache area. When the character image data to be imaged is in the cache area (when it hits), it is possible to reuse the character image data. When the character image data to be imaged is not in the cache area (when a cache failure occurs), character image data is newly generated.